Textile material of comparatively low electric resistance and method of producing the same



iatented June :2, 1948 TEXTILE MATERIAL OF COMPARATIVELY I LOW ELECTRIC RESISTANCE AND METH- OD OF PRODUCING THE SAME Kenneth n. Barnard, Short Hills, N. 1., Jayson o. Balsbaugh, Newton, Mass, and Melville J.

Blackwood. Maplewood, N. .L, assignors to Pacific Mills, Boston, Mass., a corporation of Massachusetts No Drawing. Application April 7, 1944, Serial No. 530,050

(Cl. 117-160A) 10 Claims. 1

Our invention relates to fibrous textile material, such as cloth, yarns or raw stock, permanently loaded with a finely divided electrically conductive substance, preferably a ground carbenzyl ammonium chloride based on the total weight of the impregnating bath.

After such impregnation, the material is squeezed to about 100% absorption of solution bonaceous substance suci;1 as (284F130?! blacktgr 5 an gglrigg. t i H m 1 t d with re. hite, and to the met d 0 pro uc ng e e rou's ma era en mpregna e s am za. Our treated material has a resistance in a stabilized aqueous dispersion of an electrically 1 g?" i f i i i 3 firlf iii si fiifiifii iirtfifiiil ii iiftftnyf same materia n a ry un rea e s a e an a correspondingly increased conductance. such as colloidal carbon black or graphite, as such.

The object of the invention is to provide such u t v u t e an electrically conductive fibrous material, which i g gc lf lg f ig l a 3 1 a P 312 3;- has many uses ze s um sa 0 a y nap aene s o c such material in Sheet fo m may be used to acid (in which the alkyl groups are limited to prevent or inhibit the generation and/or the $110115 Chain p We use 4% to 15% of accumulation of static electricity in articles from stablhzmg agent according to the particle $126 which the discharge of sparks might cause seri- 0f the carbon black- For p if t e b ack ous explosions, as for example, transmission belts is comparatively e diameter of its parand shoes in industrial plants which manufacture ticles averaging to micron. we ave explosives, shoes in hospital operating rooms found t 0% to 15% of the polymerized Sodium where there are explosive anaesthetic fumes, and salt of alkyl naphthalene suhomc acid, based on in the form of sheets or yarns in tires on trucks the Weight of the black, should be dissdved in the carrying gasoline or other explosives, in hose water 111 which the black 15 t0 be dispersedand carrying gasoline and in many like Situations. if the black is coarser, its particle diameter av- A preferred method of producing such elecerasing about 0-028 micro!" we use 4% to trically conductive material is as follows: We have found that the carbon black in the Fibrous material is first substantially freed of ture is largely in clusters of which the diameters an impurities, as by boning bleaching and vary from the ultimate particle size of the black thoroughly washing although this is not to a maximum of 30 microns. essary in an 58$ The mixture of stabilizing agent, carbon black The fibrous material is impregnated with a and water is ground in a pebble or colloid mill until the clusters of carbon black are broken up cationic agent of positive electrical charge. The e that the d! t of b t nu n u i th cationic material may be, for example, an amine 1 th er su a o em compound an ammonium compound, or a sul- 958 an 2 microns e mzing agent increases the negative electric charge normally fmium compomd or a phosphomum compound found on carbon black or raphite in water orthe like. We have obtained very good results g dispersion so that this charge will keep the black with tetra alkyl quaternary ammonium halides particles from undue coalescing after they have and Particularly with f' behz'yl once been dispersed by mechanical action of the monium chloride. By this impregnation, the 40 pebble or colloid m fibers are given a positive electric charge whereby 'w h found th t h the fabri is 1 they a an amhity for the conductive pregnated with this mixture the clusters of black, stance. which is electro-negatively charged and being less than 12 rnjcron m diameter penetrate with which the textile material is to be loaded. b t the fibers, which are spaced apart from The maximum amount of cetyldimethyl benzyl 3 t 12 microns, and become permanently 1 ammonium chloride On a d y basis adsorbed by bedded in the fabric by the agglomerating action ce u ose fab c is ut that is, 3% of a of the positively charged cationic agent, which water dispersion of 25% concentration. We have increases the size of the clusters so that they are found that the adsorption of t e cationic agent larger than the interfiber spaces and are thus on cellulose is practically constant and that the imprisoned in the iabric. amount reacted does not depend upon the con- The fabric is given several washes in warm centration, providing sufllcient is available. The water whereby the excess carbon black covering concentration only aifects the rate of reaction, the outer surfaces of the fabric and the not truly so for practical operating speeds we use 2% of adsorbed particles of black are washed oil. t e ori inal water d persion of cetyl di t y The impregnated fabric is squeezed and then dried. This drying operation further fixes the adsorbed black so that it is eifectively and permanently fixed on and between the fibers. By "permanently fixed we mean that the adsorbed black is not removed by water or solvent washes.

According to our research the operation is as follows: The fibers of the material, normally negative in electric charge, are made positive by the cationic agent. The carbonaceous substance and the stabilizing agent, in aqueous dispersion, are ground in water until substantially all of the clusters of the substance are reduced to less than 12 microns in diameter. The stabilizing agent increases the negative charge of the particles of the carbonaceous substance so that they are mutually repellent and thereby assists in inhibiting the coalescence of the particles and clusters. When the material is soaked in the dispersion, the clusters .penetrate between its fibers. The cationic agent reduces the negative charge, or neutralizes it, on some of the carbonaceous particles so that the particles, not being so completely of the same charge, attract one another and agglomerate into clusters which are so large that they are imbedded in between the fibers of the fabric and are not dislodged in normal use. The material thereby becomes permanently loaded with the carbonaceous substance to an amount, if desired. up to 10% of the weight of the dry untreated fabric according to the amount of the carbonaceous substance in the impregnating dispersion and the degree of discharge of the particles.

The impregnated fibrous material may be starched, dried and calendered if certain finishes or hand are desired.

The following examples are illustrative of preferred methods according to our invention.

Example 1.--A,cotton cloth (38%" 64 x 60- 5.35 yards per pound) thoroughly cleaned by boiling, bleaching and washing is treated with a hot solution of 1% acetic acid to insure that the cloth is not alkaline. It is soaked in a 2% aqueous solution of cetyl dimethyl benzyl ammonium chloride for five minutes at 100 F., with constant agitation. The cloth is squeezed to contain about its own weight of solution and dried until dry to the touch.

We prepare an aqueous dispersion of carbon black by grinding in a ball mill a mixture in water of carbon black, of an average particle diameter of about .016 micron, and of 10% of a polymerized sodium salt of alkyl naphthalene sulfonic acid to the weight of the black until the diameters of substantially all of the clusters of carbon black are less than 12 microns.

The cloth, which has been treated with cetyl dimethyl benzyl ammonium chloride, is immersed with agitation in a aqueous dispersion of this mixture at about 100 F. for five minutes, thereby thoroughly soaking the cloth with the dispersion. It is washed in warm water to remove loose carbon black, squeezed and dried.

We prefer carbon black of small particle size of an average diameter of .015 to .0175 micron because the electrical conductivity of carbon black in general increases as the particle size diminishes.

Example 2.A light weight rayon cloth is cleaned of spinning oils and extraneous materials by washing in hot soap and soda and rinsing in water to remove all impurities by well known methods. The cloth is treated with 1% acetic acid to acidify it. It is then treated with a 1% solution of cetyl dimethyl benzyl ammonium chloride for 15 to 20 minutes in along bath where the ratio of liquor to goods is kept at about 30 to 1. The cloth is squeezed to remove excess liquor and dried. The cloth is runin a bath of the same dispersion of carbon black as in Example 1, in which there are 30 parts of liquor to 1 part of cloth, for 5 minutes to completely wet the cloth and cause it to adsorb the particles of black. The cloth is washed in four warm water washes to remove excess black, then squeezed and dried.

Example 3.-A light weight cotton cloth is boiled and washed in the usual manner to thoroughly clean it. It is treated with 2% acetic acid in a padder by dipping and squeezing in the usual manner. It is padded with 5% cetyl dimethyl benzyl ammonium chloride by dipping, squeezed, and dried at high speed as in the usual method for finishing cotton cloth. The cloth is then run back and forth for 10 minutes through a jig containing a bath of 10% graphite, in place of carbon black, dispersed with polymerized sodium salt of alkyl naphthalene sulfonic acid, as described in Example. 1. The cloth is washed with several washes, squeezed and dried in a continuous manner as in' cotton finishing.

Example 4.A skein of 22's cotton yarn of normal twist, about twenty turns to the inch, is

immersed in a 2% solution of cetyl dimethyl benzyl ammonium chloride at F. in which the weight ratio of liquor to yarn is approximately The skein is turned and moved continuously to agitate the liquor for 15 minutes. The skein is removed from the liquor and centrii'uged to remove excess solution and then dried at 220 1'. until dry to the touch. It is then immersed in a bath at 100 F. of a 5% dispersion of carbon black, made according to the method set forth in Example 1, in which the ratio of liquor to skein weight is approximately 200 to 1. The skein is moved continuously in the bath for 15 minutes. It is then washed in four rinse waters at room temperature, centrifuged and dried at 220 F. until dry to the touch.

The loaded blacked fabric may be impregnated and/or coated with starch. resin or other materials and calendered or not depending upon the final use to be made of the treated fabric. Or the blacked fabric may be left without further finishing as the final use demands.

Any kind of fibrous textile may be treated by our method, above described, including cotton, wool and synthetic fibers such as rayon or the like.

The preferred negatively charged conducting substances with which the fibrous material is impregnated are finely divided, or ground, carbon black and graphite, but other conducting substances having similar properties, such as finely divided metal particles, may be used in combination with the carbon black or graphite, or alone, provided they are semi-colloidally dispersed and of clusters less than 12 microns in diameter.

The conductive fibrous material in appropriate form made by this process may be used as the outside or inside of an article or portion thereof, for example, the outer layer of a transmission belt or the inner sole of a conductive shoe. Or. the conductive fibrous material may be imbedded in another article, as for example, conductive tire cords in the tread or the wall structure of tires. Our conductive material in the latter case is most effective when the material of the article, in which it is imbedded, is also conductive, such for example, as electro-conductive rubber.

This application is a continuation-in-part of our application, Serial Number 432,904, filed February 28, 1942, now abandoned.

We claim:

1. A treated fibrous textile material having permanently reduced electrical resistance less than mm of its electrical resistance in its dry untreated state. containing a reaction product of an acidified fibrous cellulosic textile material and cetyl dimethyl benzyl ammonium chloride, and clusters exceeding 12 microns in diameter of carbon particles permanently embedded in said material, said textile material being substantially free of unfixed carbon particles removable by washing.

2. In the art of loading fibrous textile material with carbon particles to decrease the electrical resistance of the textile material, the method of improving fixation of the carbon particles in the fibrous material and thereby imparting permahence to the reduced electrical resistance thereof, comprising grinding agglomerated clusters of carbon particles in aqueous dispersion in the presence of 4% to of a salt of a polymerized short-chain-alkyl naphthalene sulfonic acid by weight of the carbon particles, until substantially all of said clusters are reduced to less than 12 microns in diameter and then immersing in said dispersion a fibrous textile material, the fibers of which bear an impregnation of about 2% by Weight of said fibers of cetyl dimethyl benzyl ammonium chloride, thereby causing the dispersed clusters of negatively charged carbon particles to penetrate between the fibers of the textile material and there be agglomerated into clusters having diameters exceeding 12 microns, washing unfixed carbon particles from said textile material and drying said material.

3. In the art of loading fibrous textile material with carbon particles to decrease the electrical resistance of the textile material, the method of improving fixation of the carbon particles in to the fibrous material and thereby imparting permanence to the reduced electrical resistance thereof, which comprises grinding agglomerated clusters of negatively charged carbon black particles in aqueous dispersion in the presence of 4% to 15% of a salt of a polymerized shortchain-alkyl naphthalene sulfonic acid by weight of the carbon particles until substantially all of said clusters are reduced to less than 12 microns in diameter. preparing a cellulosic fabric by acidifying the cellulosic material thereof and then impregnating it with cetyl dimethyl benzyl ammonium chloride, immersing the prepared fabric in said dispersion thereby causing the dispersed clusters of negatively charged carbon particles to penetrate between the fibers of the textile material and there be agglomerated into clusters having diameters exceeding 12 microns, washing out unfixed carbon particles, and drying said material.

4. In the art of loading fibrous cellulosic material with carbon black to decrease the electrical resistance of the fibrous cellulosic material. the method of improving adherence of the carbon black to the fibrous material and thereby imparting permanence to the'reduced electrical resistance thereof which comprises grinding agglomerated clusters of negatively charged carbon black particles in aqueous dispersion in the presence of a salt of a polymerized short-chainalkyl naphthalene sulfonic acid to inhibit the agglomeration of said clusters. until substantially all of said clusters are reduced to less than 12 6 microns in diameter, preparing a fibrous cellulosic fabric by acidifying the cellulosic material and then reacting cetyl dimethyl benzyl ammonium chloride therewith, immersing the prepared fabric in said dispersion thereby causing the dispersed clusters of negatively charged carbon black particles to penetrate between the V fibers of the fibrous material and there be agglomerated into clusters having diameters exceeding 12 microns, Washing and drying said material. 1

5. A treated fabric having an electrical resistance less than Aomn of the electrical resistance of the fabric when dry and untreated, comprising a fibrous textile material and up to 10% of the weight of thedry untreated fabric of clusters greater than 12 microns in diameter of carbon particles, averaging not more than 0.028 micron in diameter, permanently fixed between the fibers of said fabric, said fabric being substantially free of unfixed carbon particles removable by washing.

6. The fabric specified in claim 5 having a coating of starch thereon.

7. The fabric specified in claim 5 having a coating of resin thereon.

8. A treated fibrous textile material having an electrical resistance less than /1o.0n0 of the electrical resistance of the fibrous textile material when dry and untreated, comprising a fibrous textile material of which fibers are spaced not more than 12 microns apart and carbon particles averaging not more than 0.028 micron in diameter and being in clusters permanentl fixed between the fibers of said fibrous textile material and of sizes greater than the spaces between the fibers, said fibrous textile material being substantially free of unfixed carbon particles removable by washing.

9. In the art of loading fibrous textile material with carbon particles to decrease the elec-. trical resistance of the fibrous textile material, the method of improving fixation of the carbon particles in the fibrous material and thereby imparting permanence to the reduced electrical resistance thereof which comprises grinding agglomerated clusters of negatively charged carbon particles in aqueous dispersion in the presence of a salt of a polymerized short-chain-alkyl naphthalene sulfonic acid to inhibit the agglomeration of said clusters, until substantially all of said clusters are reduced to less than 12 microns in diameter, preparing a fibrous textile fabric by acidifying the cellulosic material thereof and then reacting cetyl dimethyl benzyl -ammonium chloride therewith, immersing the prepared fabric in said dispersion thereby causing the dispersed clusters of negatively charged carbon particles to penetrate between the fibers of the fibrous material and there be agglomerated into clusters having diameters exceeding 12 microns. washing unfixed carbon particles from the textile material and drying said material.

10. A treated fibrous textile material having an electrical resistance less than Vmbnn of the electrical resistance of the fibrous textile material when dry and untreated. comprising a fibrous textile material substantially free of unfixed carbon particles removable by washing and containing up to 10% of the weight of the-dry untreated fibrous textile material of carbon particles averaging not more than 0.028 micron in diameter, said particles being in clusters comprising sizes greater than the interfiber spaces of said fibrous textile material and thereby being 8 permanently fixed between the fibers of said Number Name Date fibrous textile material. 1,686,063 Benbow Oct. 2, 1928 KENNETH H. BARNARD. 2,338,480 Auxier Jan. 4, 1844 JAYBON C. BALSBAUGH. MELVILLE J. BLACKWOOD. 5 FOREIGN PATENTS REFERENCES CITED Number Country Date 483,496 Great Britain Oct. 22, 1938 The following references are of record in the file Of Pawn OTHER REFERENCES UNITED STATES PATENTS Harold, The Rubber Age, London, Oct. 1939, Number Name Date pages 1,327,904 Carter Jan. 13, 1920 

